An X-ray CT apparatus includes an X-ray source and an X-ray detector, which are opposedly disposed with an object interposed therebetween. The X-ray detector includes a plurality of channels (M channels) of detection elements along a direction perpendicular to a longitudinal direction of a top board (a channel direction), which is a body-axis direction.
Although various types of X-ray detectors are available, it is general in an X-ray CT apparatus to use a scintillation detector which is downsizable. Each detection element of the scintillation detector includes a scintillator and an optical sensor such as a photodiode (PD). The scintillator absorbs an X-ray collimated in a previous stage, causing a generation of fluorescence by the absorption. The PD converts the fluorescence into an electric signal by an optical sensor, and outputs it to a data acquisition system (DAS).
That is, according to the X-ray CT apparatus, an X-ray beam is radiated in a fan shape to a section of the object (hereafter, referred to as a slice surface) from the X-ray source, and the X-ray beam that has transmitted a slice surface of the object is converted into an electric signal for each detection element of the X-ray detector, thereby collecting transmission data.
Moreover, examples of the X-ray CT apparatus include a single-slice X-ray CT apparatus and a multi-slice X-ray CT apparatus. The above described X-ray CT apparatus, which includes M channels of X-ray detectors along the channel direction, and one row of them in the body-axis direction, is called a single slice X-ray CT apparatus.
In contrast, a multi-slice X-ray CT apparatus is configured, compared with the single-slice X-ray CT apparatus, such that the X-ray detector includes, in addition to M channels of detection elements, a plurality of rows (N rows) of detection elements along the direction of body axis of the object. That is, the X-ray detector of the multi-slice X-ray CT apparatus is configured to be a two-dimensional detector for X-ray CT having M channels by N rows of detection elements as a whole.
By the way, in a conventional multi-slice X-ray CT apparatus, X-ray detectors each having M channels by N rows of detection elements are arranged in the channel direction and in the body-axis direction to form an X-ray detection unit for detecting an X-ray by X-ray detectors and DASs. Moreover, the X-ray detector and the DAS are separately constructed and connected by a flexible cable.
In such X-ray detection unit, due to a recent trend of increasing the number of rows of the X-ray CT apparatus, the number of detection elements per a system has remarkably increased. Therefore, to process increased output signals of the X-ray detection unit, it is necessary to efficiently dispose ADC chips included in the DAS for processing the output signals. Moreover, if a shift of trend toward higher resolution occurs in the future, the X-ray detection unit is expected to have an even larger number of detection elements.
Meanwhile, in a conventional connection method, since there is an upper limit in the mounting area and volume in a substrate for mounting detection elements, when mounting an ADC substrate equipped with ADC chips, there is a restriction in the number of them that can be mounted. Moreover, even if an ADC substrate can be mounted, a problem exists in that the distance of the signal wiring from the detection element to the ADC substrate becomes too large so that the signal becomes subject to external noise and also the certainty of the signal deteriorates.